Automatic pressure-retaining valve.



PATENTED OCT. 16

A. ASHCRAPT.

AUTOMATIC PRESSURE RBTAINING VALVE.

APPLIQATION FILED NOV. 29. 1905.

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UNITED sTATEs PATENT oEEroE.

ALONZO ASHORAFT, OF FORT SMITH, ARKANSAS.4

AUTOMATIC lP'R'E'SSUFRE--R-El'AlNlNC V-ALV E'.

fSpeci'catiuan of Letters Patent.

Patented Oct. I6, 1906.

Application led November 29, 1.905. Serial No. 289,616.

.'Z'o :@Z whom, t may concern:

Be it know-n that I, ALONZO AsHcRAET, a citizen of the United States, residing at Fort Smith, in the county of Sebastian and State of Arkansas, have invented -a new and useful Improvement in Automatic Pressure-B etaining Valves, of which the following is a specification..

My invention relates to improvements in automatic pressure-retaining valves and is designed to take the place of the well-known hand operated pressure retainer, its object being to automatically retain a predetermined amount of braking pressure in the brake-cylinder of a car, locomotive, or tender, and to produce a device'which shall be absolutely under the control of the engineer.

A further object is to produce a device whereby the engineer may when on a long downgrade by simply moving a conveniently-located lever in the engine-cab put all retainers in operation, so that when he applies the brakes and again releases ten or fifr teen pounds of braking pressure will be retained in the brake-cylinder, the amount desired being regulated by a Westinghouse or other reducing-valve conveniently located in the engine-cab. The hand-retainers now in use retain fifteen pounds pressure. This amount may be varied, however, as before stated, by a reducing-valve, which will be explained later.

To these ends my invention consists in certain novel features of construction, arrangement, and combination of parts, as will be I hereinafter fully described, and pointed out in the claims, reference being had to the accompanying drawings, in ,which- Figure l is a sectional view of the device when the retaining-valve is not in use. Fig. 2 is a similar view as in use.

In carrying out my invention I use a valvecasing A, having differential aread chambers A and A2, one of said casings being placed under each car, connected at their lower ends with a pipe B, preferably one-half inch in diameter, and at their upper ends by a pipe C with the exhaust-port of the ordinary triple valve. The pipes B, which extend the full length of each car, are connected at each end by the ordinary air-hose and couplings, forming a continuous train-line pipe. The pipe B also extends into the locomotive-cab, where it is connected with the main reservoir.

Within the casing is fitted a piston D, that is provided with the heads D and D2, preferably of diiierent areas. 'The larger head D" fits snugly in the lower chamber A and the upper head D2 fits in the same manner in the upper chamber A2, the two heads being connected, as stated, by the common piston-rod.

In the side wall of the upper chamber near its lower end is drilled a port or opening A5, which communicates with the atmosphere.

Within the pipe B and conveniently located in the engine-cab is placed an ordinary three-way cock E, provided with a handle E and tting wi-thin the casing E2, which is provided with an exhaust-port or bleeder E3 to the atmosphere. The three-way cock is provided with the passages E4 and At a suitable point in the pipe B in the engine-cab between the three-way cock andmain reservoir is placed a reducing-valve of any suitable construction.

When the retainers are not in use, the handle E of the three-way cock is to be left parallel with the casing E2 of the three-way cock, allowing passage E5 to coincide with pipe or passage B and passage E* to coincide with passage or port E3, thereby cutting the flow of air from main reservoir and opening pipe B to the atmosphere. While the handle E is in the ab ove-mentioned position, thepistonheads D and D2 of the automatic retainervalve will be down in position, as shown in Fig. l. When the brakes are released, the pipe C being connected with the triple-valve exhaust-port, exhausted air from the brakecylinder will pass through pipe C into chamber A2, and thence to the atmosphere through port A3, which will allow all the air to exhaust from the brake-cylinder and result in a full release of the brakes. Now on a long downgrade the engineer wishes to retain, say, iifteen pounds braking pressure in all brake-cylinders after the brakes have been released. This retained pressure is wanted and on mountain roads .is absolutely necessary for the purpose of holding the trainin check until the auxiliary reservoirs are fully recharged. The handle E is then placed at right angles to casing E2 in the position shown in Fig. l, and as there is a reducing-valve located at the point X between the three-Way cock and the main reservoir he sets to reduce pressure to ive pounds. Then air-pressure to the amount of five pounds to the square inch is now allowed to pass through passage E4 and pipe B under the cars and into chamber A of the retainer-valve, forcing pistonhead D to the upper end of chamber A', caus- IOO IIO

ing piston-head D2 to pass above the port A3,. thus cutting 0H communication between the pipe C and the atmosphere. The large pistonhead D has an area of three sqkuare inches, and there n ow being a pressure oi five pounds to the square inch in chamber A there will be a total pressure of fifteen pounds, tending to hold the piston-head D up in the position just mentioned. Now when the brakes are set there is about fifty pounds air-pressure to the square inch in the brake-cylinders. The engineer releases the brakes, and this pressure of iiity pounds is permitted to vpass by means of the triplo valve into the pipe C and thence to the retainer-valve where it comes in contact with the piston-head D2. `This pistonhead has an area of one square'inch. Hence there is now a tot al pressure of fifty pounds on the small head D2 and a total pressure of fifteen pounds under the lower piston-head D. The pistons will accordingly be forced downwardly to the position shown in Fig. 1, allowing air to pass through port A3 to the atmosphere until pressure in chamber A2 is reduced to fifteen pounds, when the pistons will be equally balanced, and further reduction in the chamber A2, which will continue as long as port A3 is open, will allow pressure in chamber A to force the pistons upwardly, carrying the piston-head D2 to the upper end of chamber A2, cutting oif port A3, thereby retaining the remaining pressure in the brake-cylinder. Now to cut the retainer out of service the handle E is moved parallel with the body of the casing of the three-way cock, which not only cuts off air coming through the reducing-valve, but as passage E5 now coincides with the passage or pipe B and passage E4 with outlet-port E air is permitted to escape from chamber A and pipe B to the atmosphere, which allows piston D2 to assume the lowermost position. (Shown in Fig. l.)

. It is not absolutely necessary that the piston-heads shall be differential in area, as they may be of equal area; but the advantage of having the lower head of three times the area of the one in chamber A2 is that it is only necessary to draw on the main reservoir for onethird the amount of air-pressure that is desired to be,y retained in the brake-cylinder. The operation of cutting in and cutting out all ofthe retainers, and they may be left on as long as desired, has only cost an expenditure of main-reservoir air of a volume equal to the combined volume of the one-half-inch pipe and chamber A at iive pounds pressure. If

theV piston-heads were of equal size, it would have cost approximately three times as much as 'it did with the pistons related as shown.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. In a Huid-pressure brake system comprising a main reservoir and triple valve, the combination with a line of piping connecting said reservoir with the exhaust of said triple valve, of a valve-casing interposed in said casing intermediate the main reservoir and ltriple-valve exhaust, said casing comprising two chambers, a solid double-headed pistonvalve fitted to reciprocate in said casing within the two chambers, and a reducingvalve interposed in the piping between the main reservoir and the double-headed piston.

2. In a fluid-pressure brake system, comprising a main reservoir and a triple valve, the combinationwith a line of piping connecting the reservoir with the exhaust of the triple valve, of a valve-casing interposed in said piping betweenthe triple valve and main reservoir, said casing comprising two chambers of different areas, the smaller-aread chamber being the nearer to the triple-valve exhaust, and having an outlet to the atmosphere at or near its lower end, a piston-rod within said valve-casing, solid piston-heads at each end of said piston-rod of different area, the smaller piston-head itting in the smaller chamber, a reducing-valve interposed in the piping between the valve-casing and the main reservoir, and means for cutting in and out the valve-casing with the main reservoir.

3. In a fluid-pressure brake system, comprising a main reservoir and a triple valve, of a line of piping connecting the reservoir with the exhaust of the triple valve, a valve-casing interposed in said piping between the triple valve and the main reservoir, said casing consisting of an upper and a lower chamber, the upper chamber having an outlet- IOO port to the atmosphere at or near its lower end, a double-headed solid piston, itted to slide in said upper and lower chambers, threeway cock interposed in the piping between the retainer-valve and the main reservoir, and a reducing-valve interposed between the three-way cock and the main reservoir.

ALONZO ASHCRAFT.

Witnesses:

JOHN S. WREN, GEO. H. LYMAN. 

